U.S. Pat. No. 9,174,818 is hereby incorporated herein by reference and discloses a marine engine having a cylinder block with first and second banks of cylinders that are disposed along a longitudinal axis and extend transversely with respect to each other in a V-shape so as to define a valley there between. A catalyst receptacle is at least partially disposed in the valley and contains at least one catalyst that treats exhaust gas from the marine engine. An exhaust conduit conveys the exhaust gas from the marine engine to the catalyst receptacle. The exhaust conduit receives the exhaust gas from the first and second banks of cylinders and conveys the exhaust gas to the catalyst receptacle. The conduit reverses direction only once with respect to the longitudinal axis.